1. Field of the Invention (Technical Field)
The present invention relates to a method and apparatus for thinning crops. More particularly, the present invention relates to a method and apparatus for selectively thinning row type crops.
2. Description of Related Art
Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
Today's agriculture has become a highly competitive industry. Historically, agricultural producers in other crops have converted from hand labor to mechanization in order to be more competitive. Increased technology and automation are thus needed to compete globally.
A common practice in crop production (e.g. chile production) is to over plant the desired population counts by as much as 1000% because potential weather damage and disease losses can reduce plant populations. Once the plants are established the stand must be thinned to a desired uniform spacing for maximum yields to be obtained. It is important to thin commercial crops (e.g. chile crops) so that plant growth is not inhibited by lack of space between plants. Growers deem optimum spacing to be about two to twelve inches between plants.
The cost of hand thinning is steadily increasing due to the declining availability of laborers and also due to increases in government labor regulation on migrant workers. The high cost of hand thinning increases the cost of crop production, making it harder for farmers to compete with foreign growers who have low labor costs.
Many vegetable/fruit crop industries thin plants mechanically. Mechanical thinning has been used in some crop industries, such as the sugar beet industry, to cut hand labor costs, thus increasing profitability.
Mechanical thinning has also been used to increase plum, peach, and nectarine production as well as cutting down on extra thinning costs by topping and hedging orchards during the first and second seasons of growth (Klassen, P. “Radical Approach Cuts Pruning Costs.” Western Fruit Grower 107(11) (1987), 24–25).
The main reason for mechanical thinning is labor cost reduction. According to Baugher, Elliot, and Leach (Baugher, T. A., Elliott, K. C., and Leach, D. W., “Improved Methods of Mechanically Thinning Peaches at Full Bloom.” Journal of the Society for Horticultural Science 116(5) (1991), 766–769), during three years of research with the mechanical thinning of peaches, mechanical thinning not only increased the size of the fruit from 10% to 20%, but also afforded the grower the opportunity to decrease a major growing expense, namely hand thinning. The studies have shown that the hand-thinning requirement can be reduced by 40% to 100%. The cost of hand labor has gone up considerably in the last five years. In the United States, hand thinning costs approximately $70.00–$150.00/acre. With mechanization, labor costs can be reduced to about $8.00/acre.
In the grape industry, mechanical thinning is used to increase the production of Concord grapes. Two pruning cuts with a harvester that uses many long, thin rods that help to avoid excessive leaf thinning is driven at 1 mph (Pool, R. M. “Thin Grapes Mechanically.” Western Fruit Grower 107(10) (1987), 17–19). The color in the fruit from the mechanically thinned trees is improved because the mechanically thinned trees allow more sunlight to penetrate the trees. By allowing the grower to control the crop size with mechanical thinning, the grower able to grow large crops, while still attaining the maturity level demanded by the buyer (Pool 1987).
Original mechanical thinners include the Blackwelder mechanical thinner and the Pickett Sugar Beet Manager. These thinners were designed to work independently of hydraulic solenoids or electric power. These machines are drug along the crop rows by a tractor while making contact with the ground. These machines do not use any hydraulics, nor are they electronically controlled.
Crop thinners currently available do not provide the ability to distinguish a weed from a plant which was intentionally planted. They also cannot distinguish between a healthy plant and a diseased or dead plant. For example, U.S. Pat. No. 3,512,587 to Shader, U.S. Pat. No. 3,654,998, to Shader, and U.S. Pat. No. 3,533,474, to Weeks, each disclose a plant thinning device which is not only incapable of distinguishing between healthy, unhealthy plants, and weeds, but also require two blades as well as two blade actuating assemblies for every crop row. Further, each of these devices relies on a sharp blade which is forced beneath the soil line where it remains while it is drug through the dirt, thus severing the roots of unwanted plants. Anyone who has ever attempted to maintain a sharp lawn mower blade can easily recognize the drawbacks in maintaining a sharp blade which is constantly being drug through the dirt.
U.S. Pat. No. 3,543,860, to Field, U.S. Pat. No. 3,732,931, to Field et al., and U.S. Pat. No. 3,535,403, to Cayton et al., each disclose a very complicated crop thinning device. Each device not only has several spring loaded assemblies, hydraulic, pneumatic, and electrical assemblies, but also requires two different pistons, and supporting hardware for each blade. Further, none of these devices selectively removes dead or dying crop plants, or selectively removes weeds.
U.S. Pat. No. 4,117,888, to Fuller et al. is directed toward a crop thinning device the size of a car. While the device is large and bulky and requires its own engine, the device cannot selectively remove weeds as well as unhealthy plants.
U.S. Pat. No. 3,590,925, to Troutner is directed toward a device that lacks the ability to recall anymore than one plant which has passed its sensor but not yet reached the blade. Because the device cannot remember whether individual plants, which reside between the sensor and the blade, should be kept or cut, exactly one or zero cuts can be made to crop row for distances equal to the distance between the sensor and the blade. Thus, to thin crops such that they are still relatively close to one another, the device requires a user to disassemble, modify, and reassemble it such that the sensor is very close to the blade and can thus thin crops to a relatively close spacing. Further, it is occasionally desirable to thin plants that are up to sixteen inches tall. Since plants which are uncut by the Troutner device must pass through the spoke-like blades, damage to the canopy of taller plants as they pass between the blades is highly likely. Further, since the blades are mounted on a hub-like mechanism, in order to effectively thin plants which are sixteen inches tall, and which must therefore pass therebelow, would require the device to be around forty inches tall.
U.S. Pat. No. 3,776,316 to Eberhart is directed only toward a control circuit for a crop thinning device, and not any type of device actually capable of thinning crops. It is unable to differentiate between healthy, and dead plants, or between weeds and crop plants. Further, the control circuit lacks the ability to store in memory whether individual plants should be cut or left which have passed the sensor but not yet reached the blade. Thus, any device which utilizes this control circuit will need to mount the sensor directly in front of the blade such that the crop can be thinned close together when necessary. Mounting the sensor directly in front of the blade, however, produces the problem that flying dirt and plant debris, created by the action of the blade, may unintentionally trip the sensor, thus giving false readings.
There is thus a present need for a method and apparatus which has the ability to distinguish between healthy and unhealthy plants, as well as weeds and crop plants. There is also a present need for a method and apparatus which stores into memory whether individual plants should be cut or kept which have passed the sensor, but not yet reached the blade.